title: Core temperature variation is associated with heart rate variability independent of cardiac index: a study of 278 trauma patients.
abstract: OBJECTIVE
  The purpose of this study is to determine if temperature extremes are associated with reduced heart rate variability (HRV) and "cardiac uncoupling."
  
  
  METHODS
  This was a retrospective, observational cohort study performed on 278 trauma intensive care unit admissions that had continuous HR, cardiac index (CI), and core temperature data from "thermodilution" Swan-Ganz catheter. Dense (captured second-by-second) physiologic data were divided into 5-minute intervals (N = 136 133; 11 344 hours of data). Mean CI, mean temperature, and integer HR SD were computed for each interval. Critically low HRV was defined as HR SD from 0.3 to 0.6 beats per minute. Temperature extremes were defined as less than 36°C or greater than 39°C.
  
  
  RESULTS
  Low HRV and CI vary with temperature. Temperature extremes are associated with increased risk for critically low HRV (odds ratio, >1.8). Cardiac index increases with temperature until hyperthermia (>40°C). At temperature extremes, changes in CI were not explained solely by changes in HR.
  
  
  CONCLUSIONS
  The conclusions of this study are (1) temperature extremes are associated with low HRV, potentially reflecting cardiac autonomic dysfunction; (2) CI increases with temperature; and (3) HRV provides additional physiologic information unobtainable via current invasive cardiac monitoring and current vital signs.
authors.affiliation: Department of Surgery, Wake Forest University, Winston-Salem, NC 27157, USA. Electronic address: nmowery@wfubmc.edu.
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Mowery
authors.affiliation: Department of Surgery, Vanderbilt University Medical Center, Nashville, Tenn, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Morris
authors.affiliation: Department of Surgery, Vanderbilt University Medical Center, Nashville, Tenn, USA.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Jenkins
authors.affiliation: Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tenn, USA.
authors.forename: Asli
authors.initials: A
authors.lastname: Ozdas
authors.affiliation: Department of Surgery, Vanderbilt University Medical Center, Nashville, Tenn, USA.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Norris
mesh_terms: D001831:Body Temperature / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D003422:Critical Care; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D012189:Retrospective Studies; D014947:Wounds and Injuries / Q000503:physiopathology*